Ethyl 3- and 5-Triflyloxy-1H-pyrazole-4-carboxylates in the Synthesis of Condensed Pyrazoles by Pd-Catalysed Cross-Coupling Reactions
作者:Eglė Arbačiauskienė、Gytė Vilkauskaitė、Algirdas Šačkus、Wolfgang Holzer
DOI:10.1002/ejoc.201001560
日期:2011.4
The easily obtainable title compounds ethyl 5- and 3-triflyloxy-1H-pyrazole-4-carboxylates (2 and 5) have been used as precursors in Sonogashira-type cross-coupling reactions with various alkynes to obtain the corresponding 5- and 3-alkynyl-4-(ethoxycarbonyl)pyrazoles 3 and 6. Cyclization of the latter ortho-difunctional synthons afforded different condensed pyrazoles such as pyrano[4,3-c]pyrazol-4(1H)-ones
容易获得的标题化合物 5-和 3-三氟甲氧基-1H-吡唑-4-羧酸乙酯(2 和 5)已用作与各种炔烃进行 Sonogashira 型交叉偶联反应的前体,以获得相应的 5- 和 3-炔基-4-(乙氧羰基)吡唑 3 和 6。后者邻位双官能合成子的环化提供了不同的稠合吡唑,例如吡喃并[4,3-c]吡唑-4(1H)-酮和-4(2H)-酮7和10以及1,5-二氢-和2,5-二氢-4H-吡唑并[4,3-c]吡啶-4-酮分别为9和12。三氟甲磺酸酯 2 与苯基硼酸的 Suzuki 偶联得到相应的 5-芳基吡唑。将 5-(3-氯苯基)-1-苯基-1H-吡唑-4-羧酸 (16) 与三氟甲磺酸一起加热导致意外的四环体系 18 的形成。